Low foaming waterborne coating composition and use thereof

ABSTRACT

The present disclosure is directed to a waterborne coating composition having neutral pH that is low foaming and forms dry coating layer that has high hardness and high gloss. This disclosure is further directed to a coating composition comprising a crosslinking compoent comprising: (a) one or more alkylated melamines that are essentially unreactive to a polyisocyanate; and (b) a polyisocyanate. The coating composition can be particularly suitable for vehicle coatings and other industrial or consumer applications.

FIELD OF DISCLOSURE

The present disclosure is directed to a low foaming waterborne coatingcomposition that forms a dry coating layer having high hardness and highgloss.

BACKGROUND OF DISCLOSURE

Coating can provide one or more protective layers for the underlyingsubstrate and can also have an aesthetically pleasing value. A typicalcoating finish over a substrate can comprise some or all of thefollowing coating layers: (1) one or more primer layers that provideadhesion and basic protection, and also cover minor surface unevennessof the substrate; (2) one or more colored layers, typically pigmented,that provide most of the protection, durability and color; and (3) oneor more clearcoat layers that provide additional durability and improvedappearance. A colored topcoat layer can be used in place of the coloredlayer and clearcoat layer. These coatings can be used on buildings,machineries, equipments, vehicles as automotive original equipmentmanufacture (OEM) and refinish coatings, or in other coatingapplications.

The coatings are typically formed from coating compositions which can besolvent borne or waterborne. Solvent borne coating compositionstypically contain volatile organic compounds (VOC) that are compounds ofcarbon, which can emit into atmosphere and participate in atmosphericphotochemical reactions. Many volatile organic compounds are commonlyused in industrial products or processes, such as solvents, dispersants,carriers, coating compositions, molding compositions, cleaners, oraerosols. VOCs emitted into atmosphere, such as those emitted fromcoating compositions during coating manufacturing, application andcuring process, can be related to air pollution impacting air quality,participate in photoreactions with air to form ozone, and contribute tourban smog and global warming

Waterborne coating compositions are desirable due to their low VOCcontents. However, waterborne coating compositions can have limitationsin terms of storage, processing and handling. There are continuing needsfor improved waterborne coating compositions.

STATEMENT OF DISCLOSURE

This disclosure is directed to a process for forming a coating layerover a substrate, said process comprising the steps of

A) providing a crosslinkable component comprising one or more filmforming polymers having one or more crosslinkable functional groups,wherein at least one of the one or more crosslinkable functional groupsis hydroxyl group, said crosslinkable component comprises in a range offrom 20% to 80% of water, percent based on the total weight of thecrosslinkable component;

B) providing a crosslinking component comprising: (a) one or morealkylated melamines that are essentially unreactive to a polyisocyanate;and (b) one or more polyisocyanates each having two or more freeisocyanate crosslinking functional groups;

C) mixing said crosslinkable component with said crosslinking componentto form a coating composition, wherein said coating composition isessentially free from acid catalyst;

D) applying said coating composition over said substrate to form a wetcoating layer thereon; and

E) curing said wet coating layer at a temperature in a range of from 80°C. to 200° C. to form said coating layer.

This disclosure is also directed to a coating composition comprising:

a) a crosslinkable component comprising one or more film formingpolymers having one or more crosslinkable functional groups, wherein atleast one of the one or more crosslinkable functional groups is hydroxylgroup, said crosslinkable component comprises in a range of from 20% to80% of water, percent based on the total weight of the crosslinkablecomponent;

b) a crosslinking component comprising: (a) one or more alkylatedmelamines that are essentially unreactive to a polyisocyanate; and (b)one or more polyisocyanates each having two or more free isocyanatecrosslinking functional groups;

wherein said coating composition is essentially free from acid catalyst.

This disclosure is also directed to a substrate coated with the coatingcomposition and process disclosed herein.

DETAILED DESCRIPTION

The features and advantages of the present disclosure will be morereadily understood, by those of ordinary skill in the art, from readingthe following detailed description. It is to be appreciated that certainfeatures of the disclosure, which are, for clarity, described above andbelow in the context of separate embodiments, may also be provided incombination in a single embodiment. Conversely, various features of thedisclosure that are, for brevity, described in the context of a singleembodiment, may also be provided separately or in any sub-combination.In addition, references in the singular may also include the plural (forexample, “a” and “an” may refer to one, or one or more) unless thecontext specifically states otherwise.

The use of numerical values in the various ranges specified in thisapplication, unless expressly indicated otherwise, are stated asapproximations as though the minimum and maximum values within thestated ranges were both proceeded by the word “about.” In this manner,slight variations above and below the stated ranges can be used toachieve substantially the same results as values within the ranges.Also, the disclosure of these ranges is intended as a continuous rangeincluding every value between the minimum and maximum values.

As used herein:

“Gloss” means surface gloss of a coating surface and is related to theamount of incident light that is reflected at the specular reflectanceangle of the mean of that surface. Gloss can be measured with a specularglossmeter, such as those available from Byk-Gardener, Geretsried,Germany.

“DOI” (Distinctness of Image) is a quantitative measure of coatingappearance that measures the light reflected at and around the specularreflectance angle. It can be determined according to the methoddescribed in ASTM D 5767. DOI can be measured with wave scaninstruments, such as those available from Byk-Gardener, Geretsried,Germany. DOI measures not only the amount of incident light that isreflected at the specular reflectance angle, but also the distributionof the reflected light around the reflectance specular angle, typically+1-0.3° from the specular angle. A coating surface that gives fuzzy ordistorted image generally produces lower DOI reading. A coatingreflecting 100% of lights at the specular angle gives a DOI reading of100.

The term “volatile organic compound”, “VOC”, “volatile organiccompounds”, or “VOCs” refers to organic chemical compounds of carbonthat can vaporize and enter the atmosphere and participate inatmospheric photochemical reactions. VOCs can be naturally occurring orproduced from natural or synthetic materials. Some or all VOCs can beregulated under local, national, regional, or international authorities.VOC can be expressed as weight of VOC on a unit of volume of a product,such as pounds per gallon (lbs/gal). Amounts of VOC in a coatingcomposition can be determined according to ASTM D3960.

The term “two-pack coating composition”, also known as 2K coatingcomposition, refers to a coating composition having two packages thatare stored in separate containers and sealed to increase the shelf lifeof the coating composition during storage. The two packages are mixedjust prior to use to form a pot mix, which has a limited pot life,typically ranging from a few minutes (15 minutes to 45 minutes) to a fewhours (4 hours to 8 hours). The pot mix is then applied as a layer of adesired thickness on a substrate surface, such as an automobile body.After application, the layer dries and cures at ambient or at elevatedtemperatures to form a coating on the substrate surface having desiredcoating properties, such as, adhesion, high gloss, and high DOI.

The term “crosslinkable component” refers to a component having“crosslinkable functional groups” that are functional groups positionedin each molecule of the compounds, oligomer, polymer, the backbone ofthe polymer, pendant from the backbone of the polymer, terminallypositioned on the backbone of the polymer, or a combination thereof,wherein these functional groups are capable of crosslinking withcrosslinking functional groups (during the curing step) to produce acoating in the form of crosslinked structures. One of ordinary skill inthe art would recognize that certain crosslinkable functional groupcombinations would be excluded, since, if present, these combinationswould crosslink among themselves (self-crosslink), thereby destroyingtheir ability to crosslink with the crosslinking functional groups. Aworkable combination of crosslinkable functional groups refers to thecombinations of crosslinkable functional groups that can be used incoating applications excluding those combinations that wouldself-crosslink.

Typical crosslinkable functional groups can include hydroxyl, thiol,isocyanate, thioisocyanate, acetoacetoxy, carboxyl, primary amine,secondary amine, epoxy, anhydride, ketimine, aldimine, or a workablecombination thereof. Some other functional groups such as orthoester,orthocarbonate, or cyclic amide that can generate hydroxyl or aminegroups once the ring structure is opened can also be suitable ascrosslinkable functional groups.

The term “crosslinking component” refers to a component having“crosslinking functional groups” that are functional groups positionedin each molecule of the compounds, oligomer, polymer, the backbone ofthe polymer, pendant from the backbone of the polymer, terminallypositioned on the backbone of the polymer, or a combination thereof,wherein these functional groups are capable of crosslinking with thecrosslinkable functional groups (during the curing step) to produce acoating in the form of crosslinked structures. One of ordinary skill inthe art would recognize that certain crosslinking functional groupcombinations would be excluded, since, if present, these combinationswould crosslink among themselves (self-crosslink), thereby destroyingtheir ability to crosslink with the crosslinkable functional groups. Aworkable combination of crosslinking functional groups refers to thecombinations of crosslinking functional groups that can be used incoating applications excluding those combinations that wouldself-crosslink. One of ordinary skill in the art would recognize thatcertain combinations of crosslinking functional group and crosslinkablefunctional groups would be excluded, since they would fail to crosslinkand produce the film forming crosslinked structures. The crosslinkingcomponent can comprise one or more crosslinking agents that have thecrosslinking functional groups.

Typical crosslinking functional groups can include hydroxyl, thiol,isocyanate, thioisocyanate, acetoacetoxy, carboxyl, primary amine,secondary amine, epoxy, anhydride, ketimine, aldimine, orthoester,orthocarbonate, cyclic amide or a workable combination thereof

It would be clear to one of ordinary skill in the art that certaincrosslinking functional groups crosslink with certain crosslinkablefunctional groups. Examples of paired combinations of crosslinkable andcrosslinking functional groups can include: (1) amine and protectedamine such as ketimine and aldimine functional groups generallycrosslink with acetoacetoxy, epoxy, or anhydride functional groups; (2)isocyanate, thioisocyanate and melamine functional groups generallycrosslink with hydroxyl, thiol, primary and secondary amine, ketimine,or aldimine functional groups; (3) epoxy functional groups generallycrosslink with carboxyl, primary and secondary amine, ketimine, aldimineor anhydride functional groups; and (4) carboxyl functional groupsgenerally crosslink with epoxy or isocyanate functional groups.

This disclosure is directed to a process for forming a coating layerover a substrate. The process can comprise the steps of:

A) providing a crosslinkable component comprising one or more filmforming polymers having one or more crosslinkable functional groups,wherein at least one of the one or more crosslinkable functional groupsis hydroxyl group, said crosslinkable component comprises in a range offrom 20% to 80% of water, percent based on the total weight of thecrosslinkable component;

B) providing a crosslinking component comprising: (a) one or morealkylated melamines that are essentially unreactive to a polyisocyanate;and (b) one or more polyisocyanates each having two or more freeisocyanate crosslinking functional groups;

C) mixing said crosslinkable component with said crosslinking componentto form a coating composition, wherein said coating composition isessentially free from acid catalyst;

D) applying said coating composition over said substrate to form a wetcoating layer thereon; and

E) curing said wet coating layer at a temperature in a range of from 80°C. to 200° C. to form said coating layer.

The alkylated melamines need to be essentially unreactive to apolyisocyanate. To be “essentially unreactive”, a mixture of the one ormore melamines and the polyisocyanate must stay un-gelled for at least 5hours from the time of mixing and the viscosity of the mixture remainsbelow 150% of the initial viscosity for at least 2 hours from the timeof mixing at ambient temperatures such as a temperature in a range offrom 15° C. to 60° C., wherein the initial viscosity is the viscosity ofthe mixture measured immediately after the one or more melamines and thepolyisocyanate are just mixed. The measurement needs to be done underconditions to minimize the evaporation of solvents from the mixture tominimize viscosity change caused by the loss of solvents. Thepolyisocyanate can be a diisocyanate monomer, diisocyanate dimer,diisocyanate trimer, tri-functional isocyanates, trimers oftri-functional isocyanates, or a combination thereof. The mixture canhave a weight ratio of the melamine and the polyisocyanate in a range offrom 5:1 to 1:5. In one example, a melamine can be tested for itreactivity towards a polyisocyanate by mixing 1 weight part of themelamine and 1 weight part of a polyisocyanate, such as1,6-hexamethylene diisocyanate (“HDI”) trimer and measuring theviscosity of the mixture 0, 2 and 5 hour time point from mixing atambient temperatures. The melamine can be determined as essentiallyunreactive to a polyisocyanate if the mixture is not gelled and theviscosity at 2 hour time point remains less than 150% of the initialviscosity measured at 0 hour time point. The alkylated melamines can beessentially unreactive to 1,6-hexamethylene diisocyanate (“HDI”) monomeror trimer.

Any melamines that are essentially unreactive to a polyisocyanate can besuitable. In one example, the suitable melamine can include Cymel®XW-3106, commercially available under respective registered trademark ortrademark from Cytec Industries, Inc., Wallingford, Conn. 06492, USA.The alkylated melamine can include alkylated melamine aldehydecondensation products or derivatives, such as alkylated melamineformaldehyde. In one example, the alkylated melamines that areessentially unreactive to a polyisocyanate can include fully alkylatedmelamines that are essentially free from isocyanate reactive H, such as-OH, -NH, -NH₂, or a combination thereof. The term “essentially freefrom isocyanate reactive H” means that the alkylated melamine can haveminor amounts of functional groups having the isocyanate reactive H,such as —OH, —NH, —NH₂, or a combination thereof, and a mixture of thealkylated melamine and the polyisocyanate does not form gel and thecrosslinking component can remain in a low viscosity range suitable forcoating applications, such as mixing with a crosslinkable component forspraying, rolling, brushing, dipping, draw-down, or a combinationthereof. The alkylated melamine can have in a range of from 0% to 10% inone example, 0% to 5% in another example, 0% to 1% in yet anotherexample, 0% to 0.1% in yet another example, of melamine that havefunctional groups having the isocyanate reactive H, percentage based onthe total weight of melamine in the crosslinking component. Thecrosslinking component can have in a range of from 0% to 10% in oneexample, 0% to 5% in another example, 0% to 1% in yet another example,0% to 0.1% in yet another example, of melamines having —OH, —NH, —NH₂groups, or a combination thereof, percentage based on the total weightof melamine in the crosslinking component.

The alkylated melamine can be formed by first reacting with one or moreC1-C5 aldehydes to form alcohols, and then react with one or more C1-C10alkylation agents. The alkylated melamine can comprise alkylation groupsselected from one or more C1-C10 alkyls in one example, C1-C5 alkyls inanother example. In a further example, the alkylated melamine cancomprise methyl groups. In yet another example, the alkylated melaminecan comprise butyl groups. In yet another example, the alkylatedmelamine can comprise a combination of methyl and butyl groups. Amelamine having all amine groups alkylated is referred to as a fullyalkylated melamine. Examples of fully alkylated melamine can includehexamethoxymethylmelamine (HMMM) and melamine having butoxymethylgroups, ethoxymethyl groups, methoxymethyl groups, or a combinationthereof

When a melamine is not essentially unreactive to a polyioscyanate, suchas a melamine contains the isocyanate reactive H, for example —NH or—NH₂, over the range specified above, the mixture of the melamine andthe polyisocyanate can react leading to undesired products or propertiessuch high viscosity or gelling.

The film forming polymers can be selected from acrylic polymers,polyester polymers, polyurethane polymers, alkyd resins, or acombination thereof. Typical polymers suitable for coating compositionscan be suitable.

The acrylic polymers can have a weight average molecular weight (Mw) ofabout 1,500 to 100,000, and contain crosslinking functional groups, suchas, for example, hydroxyl, amino, amide, glycidyl, silane and carboxylgroups. The acrylic polymers can be linear polymers, branched polymers,or other polymers. The acrylic polymers can be polymerized from aplurality of monomers, such as acrylates, methacrylates or derivativesthereof. Suitable monomers can include linear alkyl (meth)acrylateshaving 1 to 12 carbon atoms in the alkyl group, cyclic or branched alkyl(meth)acrylates having 3 to 12 carbon atoms in the alkyl group. Suitablemonomers can also include, for example, hydroxyalkyl esters ofalpha,beta-olefinically unsaturated monocarboxylic acids with primary orsecondary hydroxyl groups. These may, for example, comprise thehydroxyalkyl esters of acrylic acid, methacrylic acid, crotonic acidand/or isocrotonic acid. Suitable monomers can also include monomersthat are reaction products of alpha,beta-unsaturated monocarboxylicacids with glycidyl esters of saturated monocarboxylic acids branched inalpha position, for example with glycidyl esters of saturatedalpha-alkylalkanemonocarboxylic acids oralpha,alpha'-dialkylalkanemonocarboxylic acids. These can comprise thereaction products of (meth)acrylic acid with glycidyl esters ofsaturated alpha,alpha-dialkylalkanemonocarboxylic acids with 7 to 13carbon atoms per molecule, particularly preferably with 9 to 11 carbonatoms per molecule. These reaction products can be formed before, duringor after copolymerization reaction of the acrylic polymer. Suitablemonomers can further include monomers that are reaction products ofhydroxyalkyl (meth)acrylates with lactones. Hydroxyalkyl (meth)acrylateswhich can be used include, for example, those stated above. Suitablelactones can include, for example, those that have 3 to 9 carbon atomsin the ring, wherein the rings can also comprise different substituents.The hydroxyl groups of the hydroxyalkyl esters can be modified with thelactone before, during or after the copolymerization reaction. Suitablemonomers can also include unsaturated monomers such as, for example,allyl glycidyl ether, 3,4-epoxy-1-vinylcyclohexane, epoxycyclohexyl(meth)acrylate, vinyl glycidyl ether and glycidyl (meth)acrylate, thatcan be used to provide the acrylic polymer with glycidyl groups. In oneexample, glycidyl (meth)acrylate can be used. Suitable monomers can alsoinclude monomers that are free-radically polymerizable, olefinicallyunsaturated monomers which, apart from at least one olefinic doublebond, do not contain additional functional groups. Such monomersinclude, for example, esters of olefinically unsaturated carboxylicacids with aliphatic monohydric branched or unbranched as well as cyclicalcohols with 1 to 20 carbon atoms. Suitable monomers can also includeunsaturated monomers that do not contain additional functional groupsfor example, vinyl ethers, such as, isobutyl vinyl ether and vinylesters, such as, vinyl acetate, vinyl propionate, vinyl aromatichydrocarbons, preferably those with 8 to 9 carbon atoms per molecule.Examples of such monomers can include styrene, alpha-methylstyrene,chlorostyrenes, 2,5-dimethylstyrene, p-methoxystyrene, vinyl toluene. Inone embodiment, styrene can be used. Suitable monomers can also includesmall proportions of olefinically polyunsaturated monomers. Theseolefinically polyunsaturated monomers are monomers having at least 2free-radically polymerizable double bonds per molecule. Examples ofthese olefinically polyunsaturated monomers can include divinylbenzene,1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycoldimethacrylate, and glycerol dimethacrylate.

The acrylic polymers of this disclosure can generally be polymerized byfree-radical copolymerization using conventional processes well known tothose skilled in the art, for example, bulk, solution or beadpolymerization, in particular by free-radical solution polymerizationusing free-radical initiators.

The acrylic polymer can contain (meth)acrylamides. Typical examples ofsuch acrylic polymers can be polymerized from monomers including(meth)acrylamide. In one example, such acrylic polymer can bepolymerized from (meth)acrylamide and alkyl (meth)acrylates, hydroxyalkyl (meth)acrylates, (meth)acrylic acid and one of the aforementionedolefinically unsaturated monomers.

The acrylic polymers can have one or more crosslinkable functionalgroups. At least one of the one or more crosslinkable functional groupscan be a hydroxyl group.

The polyester polymers can be linear polyesters or copolyesters,branched polyesters or copolyesters, highly branched polyesters orcopolyesters, or a combination thereof. The highly branched copolyestercan have a hydroxyl number in a range of from 5 to 200 and can have aweight average molecular weight in a range of from 1,000 to 50,000.

The polyester polymers can have one or more crosslinkable functionalgroups. At least one of the one or more crosslinkable functional groupscan be a hydroxyl group.

Polyurethane polymers can be suitable for the coating composition ofthis disclosure. Examples of polyurethane polymers can includeacrylourethanes. Typical useful acrylourethanes can be formed byreacting the aforementioned acrylic polymers with an organicpolyisocyanate. Generally, an excess of the acrylic polymer is used sothat the resulting acrylourethane can have terminal acrylic segmentshaving reactive groups such as crosslinkable functional groups such ashydroxyl, carboxyl, amine, glycidyl, amide, silane, or acombinationthereof. At least one of the one or more crosslinkable functional groupscan be a hydroxyl group.

Suitable alkyd resins can include esterification products. Examples caninclude esterification products of a drying oil fatty acid, such aslinseed oil and tall oil fatty acid, dehydrated castor oil, a polyhydricalcohol, a dicarboxylic acid and an aromatic monocarboxylic acid.

The process can further comprise the steps of mixing one or morepigments, one or more solvents, ultraviolet light stabilizers,ultraviolet light absorbers, antioxidants, hindered amine lightstabilizers, leveling agents, rheological agents, thickeners,antifoaming agents, wetting agents, or a combination thereof, into saidcrosslinkable component or said coating composition.

Examples of polyisocyanates can include aliphatic polyisocyanates,cycloaliphatic polyisocyanates, aromatic polyisocyanates and isocyanateadducts. Examples of suitable aliphatic, cycloaliphatic and aromaticpolyisocyanates that can include: 2,4-toluene diisocyanate, 2,6-toluenediisocyanate (“TDI”), 4,4-diphenylmethane diisocyanate (“MDI”),4,4′-dicyclohexyl methane diisocyanate (“H12MDI”),3,3′-dimethyl-4,4′-biphenyl diisocyanate (“TODI”), 1,4-benzenediisocyanate, trans-cyclohexane-1,4-diisocyanate, 1,5-naphthalenediisocyanate (“NDI”), 1,6-hexamethylene diisocyanate (“HDI”), 4,6-xylenediisocyanate, isophorone diisocyanate,(“IPDI”), other aliphatic orcycloaliphatic di-, tri- or tetra-isocyanates, such as, 1,2-propylenediisocyanate, tetramethylene diisocyanate, 2,3-butylene diisocyanate,octamethylene diisocyanate, 2,2,4-trimethyl hexamethylene diisocyanate,dodecamethylene diisocyanate, omega-dipropyl ether diisocyanate,1,3-cyclopentane diisocyanate, 1,2-cyclohexane diisocyanate,1,4-cyclohexane diisocyanate, 4-methyl-1,3-diisocyanatocyclohexane,dicyclohexylmethane-4,4′-diisocyanate, 3,3′-dimethyl-dicyclohexylmethane4,4′-diisocyanate, polyisocyanates having isocyanurate structural units,such as, the isocyanurate of hexamethylene diisocyanate and theisocyanurate of isophorone diisocyanate, the adduct of 2 molecules of adiisocyanate, such as, hexamethylene diisocyanate, uretidiones ofhexamethylene diisocyanate, uretidiones of isophorone diisocyanate and adiol, such as, ethylene glycol, the adduct of 3 molecules ofhexamethylene diisocyanate and 1 molecule of water, allophanates,trimers and biurets, for example, of hexamethylene diisocyanate,allophanates, trimers and biurets, for example, of isophoronediisocyanate and the isocyanurate of hexane diisocyanate. MDI, HDI, TDIand isophorone diisocyanate are preferred because of their commercialavailability.

Tri-functional isocyanates also can be used, such as, triphenyl methanetriisocyanate, 1,3,5-benzene triisocyanate, 2,4,6-toluene triisocyanate.Trimers of diisocyanates, such as, the trimer of hexamethylenediisocyanate, sold as Tolonate® HDT from Rhodia Corporation and thetrimer of isophorone diisocyanate are also suitable.

An isocyanate functional adduct can be used, such as, an adduct of analiphatic polyisocyanate and a polyol or an adduct of an aliphaticpolyisocyanate and an amine Also, any of the aforementionedpolyisocyanates can be used with a polyol to form an adduct. Polyols,such as, trimethylol alkanes, particularly, trimethylol propane orethane can be used to form an adduct.

The weight ratio of the one or more melamine:the polyisocyanates can bein a range of from 1:0.1 to 1:10. The ratio of the melamine:thepolyisocyanates can be in a range of from ranges 1:0.1 to 1:10 in oneexample, 1:0.5 to 1:10 in another example, 1:1 to 1:10 in anotherexample, 1:0.5 to 1:5 in yet another example, and 1:1 to 1:5 in yetanother example.

The coating composition formed in the process disclosed herein must beat a pH in a range of from 6.9 to 8.1 and can be essentially free fromacid catalyst. Examples of the acid catalyst can be strong acids and canbe selected from dodecyl benzene sulfonic acid (also referred to as“DDBSA”), dinonylnaphtalene sulfonic acid, or a combination thereof.Being essentially from the acid catalyst, the coating composition cancomprise minor amounts of acid catalysts as long as the pH of thecoating composition is maintained at a pH in a range of from 6.9 to 8.1.

The coating composition formed in the disclosed process can furthercomprise one or more pigments, one or more solvents, ultraviolet lightstabilizers, ultraviolet light absorbers, antioxidants, hindered aminelight stabilizers, leveling agents, rheological agents, thickeners,antifoaming agents, wetting agents, additional catalysts, or acombination thereof.

The crosslinkable component is waterborne and can comprise in a range offrom 20% to 80% of water, percent based on the total weight of thecrosslinkable component. Typically the crosslinkable component cancomprise in a range of from 20% to 80% in one example, 30% to 80% inanother example, 40% to 80% in yet another example, and 50% to 80% inyet another example, of water. The crosslinkable component can furthercomprise one or more organic solvents. Examples of organic solvents caninclude, but not limited to, aromatic hydrocarbons, such as, toluene,xylene; ketones, such as, acetone, methyl ethyl ketone, methyl isobutylketone, methyl amyl ketone and diisobutyl ketone; esters, such as, ethylacetate, n-butyl acetate, isobutyl acetate, and a combination thereof

The coating composition can comprises to 80% by weight, based on theweight of the coating composition, of one or more solvents, water, or acombination thereof. Typically, the coating composition can have a solidcontent in a range of from 20% to 80% by weight in one example, in arange of from 50% to 80% by weight in another example and in a range offrom 60% to 80% by weight in yet another example, all based on the totalweight of the coating composition. One or more of organic solvents,water, or a combination thereof, can be added to the coating compositionto adjust properties, such as viscosity. The coating composition cancomprise in a range of from 10% to 80% of water. Typically, the coatingcomposition can comprise in a range of from 10% to 80% in one example,20% to 80% in another example, 30% to 80% in yet another example, 40% to80% in yet another example, and 50% to 80% in yet another example, ofwater, percent based on the total weight of the coating composition.

The coating composition of this disclosure can be applied over thesubstrate using typical coating application methods or process, such asspraying, brushing, dipping, roller coating, drawn down, or acombination thereof, as known to or developed by those skilled in theart. The substrate can be a vehicle, a vehicle part, or a combinationthereof.

The wet coating layer can be cured at a temperature in a range of from80° C. to 200° C. to form the coating layer. Typically, the substratecoated with the wet coating layer can be baked at a temperature in arange of from 80° C. to 200° C. in one example, 100° C. to 200° C. inanother example, 120° C. to 200° C. in yet another example, 140° C. to200° C. in a further example, and 160° C. to 200° C. in yet a furtherexample.

This disclosure is also directed to a coating composition. The coatingcomposition can comprise:

a) a crosslinkable component comprising one or more film formingpolymers having one or more crosslinkable functional groups, wherein atleast one of the one or more crosslinkable functional groups is hydroxylgroup, said crosslinkable component comprises in a range of from 20% to80% of water, percent based on the total weight of the crosslinkablecomponent;

b) a crosslinking component comprising: (a) one or more alkylatedmelamines that are essentially unreactive to a polyisocyanate; and (b)one or more polyisocyanates each having two or more free isocyanatecrosslinking functional groups; wherein said coating composition isessentially free from acid catalyst.

The weight ratio of the melamine:the polyisocyanates can be in a rangeof from 1:0.1 to 1:10. The ratio of the melamine:the polyisocyanates canbe in a range of from ranges 1:0.1 to 1:10 in one example, 1:0.5 to 1:10in another example, 1:1 to 1:10 in another example, 1:0.5 to 1:5 in yetanother example, and 1:1 to 1:5 in yet another example.

The coating composition can be at a pH in a range of from 6.9 to 8.1.

The film forming polymers can be selected from aforementioned acrylicpolymers, polyester polymers, polyurethane polymers, alkyd resins, or acombination thereof

The coating composition can further comprise one or more pigments, oneor more solvents, ultraviolet light stabilizers, ultraviolet lightabsorbers, antioxidants, hindered amine light stabilizers, levelingagents, rheological agents, thickeners, antifoaming agents, wettingagents, or a combination thereof.

The coating composition of this invention can be formulated as aclearcoat or pigmented coating composition. The coating composition canbe used as a primer, a basecoat, topcoat, such as colored topcoat.Conventional inorganic and organic colored pigments, metallic flakes andpowders, such as, aluminum flake and aluminum powders; special effectspigments, such as, coated mica flakes, coated aluminum flakes coloredpigments, or a combination thereof can be used. Transparent pigments orpigments having the same refractive index as the cured binder can alsobe used. One example of such transparent pigment can be silica.

The coating composition of this invention can also comprise one or moreultraviolet light stabilizers. Examples of such ultraviolet lightstabilizers can include ultraviolet light absorbers, screeners,quenchers, and hindered amine light stabilizers. An antioxidant can alsobe added to the coating composition.

Typical ultraviolet light stabilizers that are suitable for thisinvention can include benzophenones, triazoles, triazines, benzoates,hindered amines and mixtures thereof. A blend of hindered amine lightstabilizers, such as Tinuvin® 328 and Tinuvin®123, all commerciallyavailable from Ciba Specialty Chemicals, Tarrytown, N.Y., underrespective registered trademark, can be used.

Typical ultraviolet light absorbers that are suitable for this inventioncan include hydroxyphenyl benzotriazoles, such as,2-(2-hydroxy-5-methylphenyl)-2H-benzotrazole,2-(2-hydroxy-3,5-di-tert.amyl-phenyl)-2H-benzotriazole,2[2-hydroxy-3,5-di(1,1-dimethylbenzyl)phenyl]-2H-benzotriazole, reactionproduct of 2-(2-hydroxy-3-tert.butyl-5-methylpropionate)-2H-benzotriazole and polyethylene ether glycol having aweight average molecular weight of 300,2-(2-hydroxy-3-tert.butyl-5-iso-octyl propionate)-2H-benzotriazole;hydroxyphenyl s-triazines, such as,2-[4((2,-hydroxy-3-dodecyloxy/tridecyloxypropyl)-oxy)-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine,2-[4(2-hydroxy-3-(2-ethylhexyl)-oxy)-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)1,3,5-triazine,2-(4-octyloxy-2-hydroxyphenyl)-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine;hydroxybenzophenone U.V. absorbers, such as, 2,4-dihydroxybenzophenone,2-hydroxy-4-octyloxybenzophenone, and2-hydroxy-4-dodecyloxybenzophenone. [69] Typical hindered amine lightstabilizers can includeN-(1,2,2,6,6-pentamethyl-4-piperidinyl)-2-dodecyl succinimide,N(1acetyl-2,2,6,6-tetramethyl-4-piperidinyl)-2-dodecyl succinimide,N-(2hydroxyethyl)-2,6,6,6-tetramethylpiperidine-4-ol-succinic acidcopolymer, 1,3,5 triazine-2,4,6-triamine,N,N′“-[1,2-ethanediybis[[[4,6-bis[butyl(1,2,2,6,6-pentamethyl-4-piperidinyl)amino]-1,3,5-triazine-2-yl]imino]-3,1-propanediyl]]bis[N,N′”-dibutyl-N′, N′″-bis(1,2,2,6,6-pentamethyl-4-piperidinyl)],poly-[[6-[1,1,3,3-tetramethylbutyl)-amino]-1,3,5-trianzine-2,4-diyl][2,2,6,6-tetramethylpiperidinyl)-imino]-1,6-hexane-diyl[(2,2,6,6-tetramethyl-4-piperidinyl)-imino]),bis(2,2,6,6-tetramethyl-4-piperidinyl)sebacate,bis(1,2,2,6,6-pentamethyl-4-piperidinyl)sebacate,bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidinyl)sebacate,bis(1,2,2,6,6-pentamethyl-4-piperidinyl)[3,5bis(1,1-dimethylethyl-4-hydroxy-phenyl)methyl]butylpropanedioate,8-acetyl-3-dodecyl-7,7,9,9,-tetramethyl-1,3,8-triazaspiro(4,5)decane-2,4-dione,and dodecyl/tetradecyl-3-(2,2,4,4-tetramethyl-21-oxo-7-oxa-3,20-diazaldispiro(5.1.11.2)henicosan-20-yl)propionate. [70] Typical antioxidantsthat are suitable for this invention can includetetrakis[methylene(3,5-di-tert-butylhydroxy hydrocinnamate)]methane,octadecyl 3,5-di-tert-butyl-4-hydroxyhydrocinnamate,tris(2,4-di-tert-butylphenyl) phosphite,1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trioneand benzenepropanoic acid, 3,5-bis(1,1-dimethyl-ethyl)-4-hydroxy-C7-C9branched alkyl esters. Typically useful antioxidants can also includehydroperoxide decomposers, such as Sanko® HCA(9,10-dihydro-9-oxa-10-phosphenanthrene-10-oxide), triphenyl phosphateand other organo-phosphorous compounds, such as, Irgafos® TNPP from CibaSpecialty Chemicals, Irgafos® 168, from Ciba Specialty Chemicals,Ultranox® 626 from GE Specialty Chemicals, Mark PEP-6 from Asahi Denka,Mark HP-10 from Asahi Denka, Irgafos® P-EPQ from Ciba SpecialtyChemicals, Ethanox 398 from Albemarle, Weston 618 from GE SpecialtyChemicals, Irgafos® 12 from Ciba Specialty Chemicals, Irgafos® 38 fromCiba Specialty Chemicals, Ultranox® 641 from GE Specialty Chemicals andDoverphos® S-9228 from Dover Chemicals.

The coating composition can further comprise additional catalysts thatcan be selected from organic metal salts, such as, dibutyl tindilaurate, dibutyl tin diacetate, dibutyl tin dichloride, dibutyl tindibromide, zinc naphthenate; compounds containing tertiary amino groups,such as, triethylamine; triphenyl boron, tetraisopropyl titanate,triethanolamine titanate chelate, dibutyl tin dioxide, dibutyl tindioctoate, tin octoate, aluminum titanate, aluminum chelates, zirconiumchelate, hydrocarbon phosphonium halides, such as, ethyl triphenylphosphonium iodide and other such phosphonium salts and other catalysts,or a combination thereof.

This disclosure is also a substrate coated with any of theaforementioned coating compositions, or a combination thereof. In onexample, the substrate can be coated one or more of the aforementionedcoating compositions sequentially. In another example, the substrate canbe coated with one or more of the aforementioned coating compositions onthe same or different portions of the substrate with one or more layers.

The coating compositions of this invention can comprise conventionalcoating additives. The aforementioned additives or a combination thereofcan be suitable. Further examples of such coating additives can includewetting agents, leveling and flow control agents, for example,Resiflow®S (polybutylacrylate), BYK® 320 and 325 (high molecular weightpolyacrylates), BYK® 347 (polyether-modified siloxane) under respectiveregistered tradmarks, leveling agents based on (meth)acrylichomopolymers; rheological control agents, such as highly dispersesilica, or fumed silica; thickeners, such as partially crosslinkedpolycarboxylic acid or polyurethanes; and antifoaming agents. Theadditives are used in conventional amounts familiar to those skilled inthe art.

The coating composition of this invention can be formulated as atwo-pack (2K) coating composition. In a typical two-pack coatingcomposition comprising two packages, the two packages are mixed togethershortly before application. The first package typically can contain thecrosslinkable component. Optionally, one or more pigments can bedispersed in the first package using conventional dispersing techniques,for example, ball milling, sand milling, and attritor grinding. Thefirst package can also comprise water, and optionally one or moresolvents. The second package can contain the crosslinking component, andoptionally, one or more solvents.

The coating composition can be further adjusted to spray viscosity withorganic solvents, water, or a combination thereof, as determined bythose skilled in the art before being applied over the substrate.

The substrate can be any articles or objects that can be coated with acoating composition. The substrate can include a vehicle, parts of avehicle, or a combination thereof. The coating composition according tothe disclosure can be suitable for vehicle and industrial coating andcan be applied using known processes. In the context of vehicle coating,the coating composition can be used both for vehicle original equipmentmanufacturing (OEM) coating and for repairing or refinishing coatings ofvehicles and vehicle parts. Curing of the coating composition can beaccomplished at temperatures in a range of from 80° C. to 200° C.

This disclosure is further directed to a substrate coated by theaforementioned process. Examples of coated substrate can include, butnot limited to: home appliances, such as refrigerator, washing machine,dishwasher, microwave ovens, cooking and baking ovens; electronicappliances, such as television sets, computers, electronic game sets,audio and video equipment; recreational equipment, such as bicycles, skiequipment, all terrain vehicles; and home or office furniture, such astables, file cabinets. In one example, the coated substrate is a vehicleor parts of a vehicle.

Applicants unexpectedly discovered that the mixture of alkylatedmelamine and polyisocyanates resulted in a coating composition formsless foam therefore more gassing resistant. The coating layer can haveimproved gloss, DOI and hardness.

Testing Procedures

Dry Film Thickness—test method ASTM D4138

Viscosity—can be measured using (1) Zahn Viscosity as determined using a#1 Zahn cup according to ASTM D 1084 Method D; (2) Gardner-Holdt Letterscale according to ASTM D1545; or (3) Brookfield viscometer; asspecified.

Tg (glass transition temperature) of a polymer is determined accordingto ASTM D-3418 (1988) or calculated according to the Fox Equation.

Molecular weights Mw and Mn and the polydispersity (Mw/Mn) of theacrylic polymer and other polymers are determined by GPC (Gel PermeationChromatography) using polystyrene standards and tetrahydrofuran as thesolvent.

Dry to touch time—Dry to touch time is determined by ASTM D1640.

Tack Free Time—Tack free time was determined with Mechanical Test Methodaccording to ASTM D 1640-95. The mechanical test method was originallydescribed in U.S. Pat. No. 2,406,989.

DOI—Instrumental measurement of distinctness of Image (DOI) gloss ofcoating surfaces is determined according to ASTM D 5767.

Gloss—measured with standard test method for specular gloss according toASTM D 523.

Hardness—Persoz hardness test is measured according to ASTM D4366.

Gassing Resistance—measured by visually observing dry coating at variousthicknesses for visible bubbles. The highest dry thickness having novisible bubbles is assigned as gassing resistance thickness of thecoating.

In the following examples, all parts and percentages are on a weightbasis unless otherwise indicated. “Mw” weight average molecular weightand “Mn” means number average molecular weight.

EXAMPLES

The present invention is further defined in the following Examples. Itshould be understood that these Examples, while indicating preferredembodiments of the invention, are given by way of illustration only.From the above discussion and these Examples, one skilled in the art canascertain the essential characteristics of this invention, and withoutdeparting from the spirit and scope thereof, can make various changesand modifications of the invention to adapt it to various uses andconditions.

Coating Compositions

Coating compositions were prepared according to Table 1 by firstpreparing the Pack 1 and Pack 2 separately and then mixing the Pack 1and Pack 2 immediately prior to applying the coating composition overthe substrate.

TABLE 1 Coating Compositions (in weight grams). Comp 1 Comp 2 ExamplePack 1: Crosslinkable Component⁽¹⁾ 15 15 15 Pack 2: Alkylatedmelamine⁽²⁾ 0 10 5 Polyisocyanate⁽³⁾ 10 0 5 Total 25 25 25 ⁽¹⁾Thecrosslinkable component used was a waterborne clearcoat Imron ® ZVHG-C ™ 572 ™ available under respective registered trademark ortrademark from E. I. DuPont de Nemours and Company, Wilmington, DE, USA.Imron ® ZV HG-C ™ 572 ™ contains about 25% of water, percentage based onthe total weight of the Imron ® ZV HG-C ™ 572 ™ ⁽²⁾The alkylatedmelamine used was Cymel ® XW-3106, available under respective registeredtrademark or trademark from Cytec Industries, Inc., Wallingford, CT06492, USA. Cymel ® XW-3106 is unreactive to 1,6-hexamethylenediisocyanate (“HDI”) trimer under the conditions disclosed herein.⁽³⁾The polyisocyanate used was a mixture of diisocyanates and aliphaticpolyisocyanates available as FG-572 ™ under respective registeredtrademark or trademark from E. I. DuPont de Nemours and Company,Wilmington, DE, USA.

Coating Properties

The coating compositions were applied on 4×12″ cold rolled steel panelscoated with Ecoat available as ACT CRS B952 Powercron 590 Ecoat from ACTTest Pannels LLC, Hillsdale, Mich., USA, using wet draw down. The wetcoating layers were baked at 285° F. (about 140° C.) for 20 min to formdry coating layers that had dry thicknesses of about 2 mils.

Coating property data are shown in Table 2. The data indicated that thecoating composition of this disclosure (Example) had better DOI, higherhardness comparing to melamine alone and less foaming (high gassingresistance).

TABLE 2 Coating Properties. Comp 1 Comp 2 Example Dry film thickness(mil)⁽⁴⁾ 2 2 2 Persoz Hardness (sec)⁽⁵⁾ 140 24 92 DOI⁽⁶⁾ 79.65 67.8271.34 Gassing Resistance (mil)⁽⁷⁾ 10 >12 >12 ⁽⁴⁾According to ASTM D4138.⁽⁵⁾According to ASTM D4366. ⁽⁶⁾According to ASTM D5767. ⁽⁷⁾Gassingresistance is defined as a dry coating thickness where no gassing orbubbles are observed in the coating. Gassing was visually observed asbubbles (size in a range of from 0.5 to 1 mm) in dried coatings. ForComp 1, bubbles were observed at 10 mil dry coating thickness, while forCom 2 and Example, no bubbles were observed at at least 12 mil drycoating thickness.

1. A process for forming a coating layer over a substrate, said processcomprising the steps of: A) providing a crosslinkable componentcomprising a film forming polymer having a crosslinkable functionalgroups, wherein the crosslinkable functional group is a hydroxyl group,and wherein the crosslinkable component comprises in a range of fromabout 20% to about 80% of water, percent based on the total weight ofthe crosslinkable component; B) providing a crosslinking componentcomprising: (a) an alkylated melamine that is essentially unreactive toa polyisocyanate; and (b) a polyisocyanate having two or more freeisocyanate crosslinking functional groups; C) mixing said crosslinkablecomponent with said crosslinking component to form a coatingcomposition, wherein said coating composition is essentially free fromacid catalyst; D) applying said coating composition over said substrateto form a wet coating layer thereon; and E) curing said wet coatinglayer at a temperature in a range of from about 80° C. to about 200° C.to form said coating layer.
 2. The process of claim 1, wherein the filmforming polymer is selected from acrylic polymers, polyester polymers,polyurethane polymers, alkyd resins, or a combination thereof.
 3. Theprocess of claim 1, wherein the alkylated melamines comprises analkylation groups selected from C1-C10 alkyls.
 4. The process of claim 1further comprising the steps of mixing a pigment, a solvent, anultraviolet light stabilizer, an ultraviolet light absorber, anantioxidant, a hindered amine light stabilizer, a leveling agent, arheological agent, a thickener, an antifoaming agent, a wetting agent,or a combination thereof, into said crosslinkable component or saidcoating composition.
 5. The process of claim 1, wherein said coatingcomposition is at a pH in a range of from about 6.9 to about 8.1.
 6. Theprocess of claim 1, wherein the weight ratio of melamine: polyisocyanateis in a range of from about 1:0.1 to about 1:10.
 7. (canceled) 8.(canceled)
 9. A coating composition comprising: a) a crosslinkablecomponent comprising a film forming polymer having a crosslinkablefunctional group, wherein the crosslinkable functional group is ahydroxyl group, and wherein the crosslinkable component comprises in arange of from about 20% to about 80% of water, percent based on thetotal weight of the crosslinkable component; b) a crosslinking componentcomprising: (a) an alkylated melamine that is essentially unreactive toa polyisocyanate, and (b) a polyisocyanate having two or more freeisocyanate crosslinking functional groups; wherein the coatingcomposition is essentially free from acid catalyst.
 10. The coatingcomposition of claim 1, wherein the film forming polymer is selectedfrom acrylic polymers, polyester polymers, polyurethane polymers, alkydresins, or a combination thereof.
 11. The coating composition of claim1, wherein the alkylated melamines comprises an alkylation groupselected from C1-C10 alkyls.
 12. The coating composition of claim 1further comprising a pigment, a solvent, an ultraviolet lightstabilizer, an ultraviolet light absorber, an antioxidant, a hinderedamine light stabilizer, a leveling agent, a rheological agent, athickener, an antifoaming agent, a wetting agent, or a combinationthereof.
 13. The coating composition of claim 1, wherein the coatingcomposition is at a pH in a range of from about 6.9 to about 8.1. 14.The coating composition of claim 1, wherein the weight ratio ofmelamine: polyisocyanate is in a range of from about 1:0.1 to about1:10.
 15. A substrate coated with a coating composition comprising: a) acrosslinkable component comprising a film forming polymer having acrosslinkable functional group, wherein the crosslinkable functionalgroup is a hydroxyl group, and wherein the crosslinkable componentcomprises in a range of from about 20% to about 80% of water, percentbased on the total weight of the crosslinkable component; b) acrosslinking component comprising: (a) an alkylated melamine that isessentially unreactive to a polvisocyanate, and (b) a polvisocyanatehaving two or more free isocyanate crosslinking functional groups;wherein the coating composition is essentially free from acid catalyst.16. The substrate of claim 15, wherein the substrate is a vehicle. 17.The substrate of claim 15, wherein the film forming polymer is selectedfrom acrylic polymers, polyester polymers, polyurethane polymers, alkydresins, or a combination thereof.
 18. The substrate of claim 15, whereinthe alkylated melamine comprises an alkylation group selected fromC1-C10 alkyls.
 19. The substrate of claim 15, wherein the coatingcomposition is at a pH in a range of from about 6.9 to about 8.1. 20.The substrate of claim 15, wherein the weight ratio ofmelamine:polyisocyanate is in a range of from about 1:0.1 to about 1:10.